[jobigoud]

Taking the change into account for the current time is relatively easy, but date/time libraries in programming languages need to be updated so that you can write a calendar application with, say, a recurring event spanning across the change, or count days since a specific date in the past.

[hyperpape]

Even with DST, the actual date DST starts differs unpredictably from year to year. I don't think this introduces any new problems.

[gsnedders]

In the EU, the start date is predictable: the last Sunday in March. The end is equally predictable: the last Sunday in October.

[hyperpape]

Interesting.

I suppose that consistency could’ve given some EU only companies enough rope to hang themselves. Really, doing things the right way is easier than hand-writing some code that assumes DST starts/ends on a fixed date—at least in a language with a real date/time library.